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Distinguishing vegetation communities
Aerial Photography for Land Cover Mapping and
Habitat Analysis
Understand the difference between land cover, vegetation, ecosystems, and habitat
Understand the general procedure used for mapping land cover using remote sensing
Understand the importance of scale and MMU.Be able to construct a classification scheme for
mapping.Understand the role of photointerpretation and
interpretation keys.Understand the importance of accuracy
assessment in mapping.
Learning Objectives
VegetationThe act or process of vegetatingAll of the plant life in a particular region (e.g., the
vegetation of Wyoming) or period (e.g., Pleistocene vegetation)
EcosystemAn interacting system of biotic (plants, animals,
microorganisms) and abiotic factors (the environment)Land Cover
All of the features occupying the land surface including vegetation, unvegetated areas, natural and human affected
HabitatHabitat includes the physical requirements that a species
requires to live.
Some definitions…
Scope the projectAcquire the aerial photography (or satellite
data)Develop a classification scheme (mapping
legend)Explore the area on the ground (if possible)Develop an interpretation keyCreate land cover units (make the map) Assess the accuracy of the productRefine as necessary
Mapping land cover: General procedure
What is the desired mapping scale?What is the MMU?What resources are available (data, money,
etc.)?How much time is available to do the project?How accessible is the map area?
Scoping the project
The minimum mapping unit is the smallest area that will be digitized or classified on your map. Very important decision because it determines
what patch sizes will be subsumed and which will be retained
Will have different effects on map depending on the spatial configuration of the area (E.g., is the area composed of large homogeneous areas or is it patchy)
Sometimes maps have different MMUs for some types (e.g., riparian) than others
MMU is limited by resolution of the imagery
Minimum Mapping Units (MMU's)
Copper Mountain, Colorado (IKONOS image)
MMU determines which clearcuts get mapped
What qualities does the aerial photography need to have to accomplish the mapping task?Dates/timesSpatial scale/resolutionSpectral resolution (panchromatic, true color, false
color IR, etc.)Geometric properties (orthorectified, vertical, oblique,
etc.)Amount of overlap for stereo viewing, etc.
Are suitable photos available (e.g., NAPP)Are contractors available to fly if no archive is
suitable?Costs, timing, etc.
Acquiring aerial photography
How many types do you want to map? How should you divide up the features you
are interested in?What resources do you have?How will your interpretation be used?What do the funders want!
Can be very controversial!
Land Cover Classification Schemes
How would you classify this produce?
• Must be useful• Types must be detectable using the
data you have• Should be hierarchical• Categories must be mutually exclusive• Require explicit definitions of each
class
Characteristics of classification schemes
I. VegetatedA. Forest
1. Evergreena. Spruce-fir forest
i. Spruce-fir with winterberry understory
b. Lodgepole pine forestc. etc.
2. Deciduous
B. Shrubland
II. Non-Vegetated
Example of a simple hierarchy
1a. Trees (woody plants usually over 5m tall) present and forming 10-100% cover. 2a. Trees with their crowns interlocking, forming 60-100% [FOREST].....................................................................3 3a. Deciduous species contribute >75% of the total tree cover Deciduous Forest 4a. Upland.............................................................................................................................5 5a. Acer saccharum dominant in the canopy................................................6 6a. Forest of sheltered hillsides or pockets (coves), with moist comparatively rich soils, sometimes bouldery; Acer saccharum usually strongly dominant; herb layer may contain rare species such as Dryopteris goldiana, Panax quinquefolius, or Impatians pallida....... Acer saccharum-Fraxinus americana-Tilia americana Forest Alliance 6b. Forest of mid-elevation slopes and ridgelines; Acer saccharum typically co-dominant with Betula alleghaniensis and/or Fagus grandifolia........................................................... Acer saccharum-Betula alleghaniensis-Tilia americana Forest Alliance 5a. Quercus rubra dominant in the canopy..............................................................................etc. 4b. Wetland..................................................................................................................etc. 3b. Deciduous species contribute <75% of the total tree cover.....................................................................etc. 2b. Trees forming open to very open strands, with crowns not usually touching........................................................etc.
1b. Trees absent, or less than 5m tall, or forming <10% cover...........................................................................................etc.
Example of a more complex scheme used in the "real world"
Critical for understanding the distribution of land cover in the real world
Helps you choose useful ancillary dataUseful for understanding aerial photos back
at the computerNice to get out once in a while
Exploring the ground (field recon)
What characteristics of this landscape might be important for making a map using aerial photography?
How would you classify this vegetation and where are the boundaries??
Interpretation keys should include the following:Explicit written description of each type in the
classificationExamples of each type as it appears in the
aerial photography being usedA list of key features of the type that can be
used to distinguish it from other typesCan take the form of a dichotomous key like you
would use for keying out plants or animalsShould be organized into an easy-to-use
notebook or in some kind of digital format (e.g., hyperlinked web key)
Interpretation keys
Classification can take two basic forms:Manual photointerpretation of the imagery
On hard copy using clear overlays or other toolsOn computer screen by digitizing with mouse
Per-pixel classification of digital imageryNot used as commonly with aerial photography
because the spectral resolution is not as good as in multispectral satellite imagery.
Will talk about this more in the context of satellite data
Photointerpretation/classification
Detailed view of Wyoming GAP Land Cover Map
Wetland community mapping – University of Wisconsin
Horticulture map at University of WisconsinIndividual shrubs delimited with carefully rectified orthophoto
Accuracy assessment is crucial for any mapping project
Requires extensive field work to compare what is on the ground to what is designated on the interpreted photo
Can be expensive – field work costs moneyCan be quantified using a suite of accuracy
assessment metrics
Assessing accuracy
If product accuracy is not sufficient must refineAssess the original data – are problems related
to the information content of the data?Assess the interpretive process – are problems
related to inconsistent or poor photointerpretation? Does the interpretive key need to be
revised/amended? Assess the classification scheme – is the list of
types appropriate and mappable.Would moving “up” the hierarchy be useful and if
so would the map still be appropriate for users?
Product refinement
Habitat is usually a combination of land cover with other spatially distributed environmental driversClimateSoilsProximity to waterAvailability of coverContiguity of cover types needed for different
parts of the life cycleAvailability of food/preyEtc.
Typically combine these as spatial layers in a GIS
Using land cover data to create habitat maps
GIS Habitat model schematic for Wild Boar
Land cover is the collection of features occupying the land surface
Air photos are useful for mapping land cover, especially at fine scales
Land cover mapping is a process with a series of important steps, each of which must be carefully executed
Our ability to accurately map land cover can be limited by the quality of the photography or other data that we are interpreting
Important to be realistic about what can be accomplished
Summary